<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
  #d1{
    width: 50px;
    height: 100px;
    background-color: red;
    position: absolute;
    z-index: 2;
  }

  #d2{
    width: 100px;
    height: 50px;
    background-color: blue;
    position: absolute;
    z-index: 1;
  }
</style>
<body>
<div id="d1"></div>
<div id="d2"></div>

</body>
</html>